import math

a = 10
b = 20
# 交换a, b的值
a, b = b, a
print("a = {}, b = {}".format(a, b))

print("-----")

a = 10
b = 20
c = 30
# 交换a, b, c的值
a, b, c = b, c, a
print("a = {}, b = {}, c = {}".format(a, b, c))

print("-----")

print(round(math.pi, 2))  # 取两位小数

# 输出:
# a = 20, b = 10
# -----
# a = 20, b = 30, c = 10
# -----
# 3.14
